Positive displacement reciprocating type pumps are well known in the art for a wide variety of applications. Reciprocating pumps are used for low to medium capacities and low to high pressures. They are useful for low- to medium-viscosity fluids, or high-viscosity fluids at materially reduced speeds. Generally, such pumps utilize one or more plungers, pistons, or diaphragms which reciprocate in a liquid chamber or cylinder. Cylinder translation is in cooperation with an inlet valve(s), which opens the cylinder to the inlet pipe during the suction stroke, and an outlet valve(s), which opens to the discharge pipe during the discharge stroke.
Reciprocating pumps may be power-driven through a crank and connecting rod or equivalent mechanism, or direct-acting, driven by steam or compressed air or gas. Reciprocating power pumps deliver essentially constant capacity over their entire pressure range when driven at constant speed. As such, the pumping capacity of reciprocating pumps is very predictable over a wide range of operating conditions.
In a typical packaging arrangement, a plurality of pumps take suction or are supplied from a common constant head. Variations in the pressure of the supply, which can be caused by a variety of factors, such as long lines, fittings, bends etc. can create poor suction conditions. A result of poor suction conditions is that the pump cylinders do not fill completely, and the pump operates less efficiently. A reciprocating pump further complicates the issue by emitting high-frequency pressure waves created by the inlet valve(s) opening and closing. For example, in high inlet pressure applications, a pump's inlet valve(s) can create "water hammer" by their opening and closing action; increasing pipe and pump damage, and decreasing system efficiency.
In high vacuum suction, lift applications, the inlet valve action actually decreases inlet fluid pressure. At suitable combinations of low pressure and high speed the pump can cavitate. Cavitation has great practical significance. It restricts the speed at which the pump may be operated and, when severe, lowers efficiency, produces noise and vibrations, and causes rapid erosion and premature failure of pump parts.
A stabilizer at the pump's inlet will act as an dampener, reducing pressure fluctuations and aid in filling the pump head with fluid during each inlet stroke. Dampeners comprising a tank and a gas filled bladder within the tank are well known for use as inlet stabilizers. However, dampeners of such construction typically operate on inlet pressure fluctuations in either the suction lift or high pressure mode but not both. Accordingly, there continues to be a need for an inlet stabilizer device for use with positive displacement, reciprocating type pumps which maintains specified flow rates during both high inlet pressure and suction lift operation.